Instrument test switch



Dec. 1, 1931. w. H. scHRAMM INSTRUMENT TEST SWITCH Filed Nov. e, 1928 INVENTOR sln.

ATT'ORNEY Patented Dec. 1, 1931 UNITED y :STATES Animation and 'Novembe My 4invention relates totest switches and particularly to switches for 'controlling current-measuring instruments and -the'like. y

An 'obj ect of 'my inventionv is 'to "provide v`a test switch that may 'be mounted *upon `a switchboard lpanel and is operable from the front `of the lswitchboard and whereinfno live parts are exposed .atthefront of the switchboard. f Y w Another object "oi my .invention vis to :provide la test switch ythat is `operable rom the front of the switchboard Vand-wherein lall test connections are. carried fby 'a test plug that 'is removably inserted in the test switch when it is -desired to make a test 'of the instrument controlled 'by the switch. p

Another object of -my invention is to provide a test switch having the `above-noted characteristics wherein the current-*controlling switch is permanently mounted in .an

enclosing unit; wherein thejt'est plug is 'provided with test contacts lthat 4engage rcontacts in the enclosing unit for connecting a test meter in the instrument `circuit and wherein the plugis provided withymeans for actuatingthe switch to open position'later the test contacts Vhave engaged `the .contacts with.- in the enclosing uni-t .and have established 'a circuit through .the test connections. y A further object of myinv'ention is "to provide an instrument `test switch wherein improper operations are precluded and wherein a test plug is provided `'that cannot he removed from the switch without first Vrestoring it toits normal operative-position.

VAnother object of `my .invention Vvis to provide a test plug'for a testswitch whereinjthe test contacts are mounted "upon conductor straps extending through the .handlev of the test plug, the .straps being of suchconstruction that desired connectionsmay he made by :joining certain of the straps at the Vends 'remote from the contacts `and .wherein 'the said ends of the conductor .straps may loe eX- posed for alterations inthe'ir connections by displacing a portion 4of v'the test-plug handle.

A further object of `my invention is rto provide .an instrument test switch that shallbe compact and inexpensive to 'manufacture and may `readily bej mounted-upon :a switch- FENNSYLVAIA, AS-SIGNOR TO WESTING- COMPANY, ,A COIRJZPORATIONy OF PENNSYL- TEST SWITCH e, 192s. serial No. A3173147:

boa-rd panel in such mannerthat it is availlable` for operation from the front oi they switchboard panel.

These and other `objects that Win be made apparent throughout 'the 'further description of my .invention are attained yby means vof the test-switch apparatus 'hereinafter -described, and lillust-rated in the accompany'-V ing drawings, wherein Figure v1 is `a lon tudinal sectional view through a'test-switch Iunit `enfibodyi-ng 'features of my invent-ion.,

Fig. 2 isa longitudinal section through a. test plug for cooperating with the test-switch unit shown in Fig. 1,

Fig. "3 is an `end view of the test switch shown in Fig. .1, Y n 4 Fig. 4 is `a longitudi-naly sectional "view,

taken von the 'line IV-TV of Fig. 1,

Fig. 5 is a transversesec'ti'onal View, taken fon the line V-V of Fig. 1,

Fig. 6 is a transverse section-al vie-W, taken on the line VI-VI of Fig. 1, V

Fig. 7 is fatransverse sectional view,talien on -the line VIIVII of Fig. l, l

p Figs.`8 Iand 9 are frontendv end elevational views, respectively, of therear end plate of the test-switch enclosure, i i

Fig.` l1() is a longitudinal section through the end plate shown in Fig. 8, taken on fthe line X-X thereof, and

Fig. .11 is a perspective View Iof the switch assembly of the test-switch unit.

Referring to th drawings, rand 4particularly to Figs. 1, 4 and 5, the test-switch unit comprisesa pairv of insulating end vplatesl 12 and 13 that are 4retained in spaced assembled relation lhymeans lof four identical and, therefore, interchangeable contact strips 14j,

15, 16 .and 17 that are provided with laterally bentends'to engage the-end plates. y The ends which engage the plate 12 are-securedthereto by screws 18 and thosewhi'ch engage `the plate 13 are secured thereto lloy terminal screws 19.'

The contact strips 14, 15, 16 andfl? are severally provided with two laterally extending wings 21 that are of such length andare sospaced apart, as indicated in 4, ithat thelintegral-contact aws with which theyare providedfare in twofsideby-side planes.

contact strips 14 and 17 carry contact jaws 22 and 23 and the contact strips 15 and 16 carry contact jaws 24 and 25. The contact jaws are thus disposed in two opposite rows having four pairs of contact jaws 22, 24, 23 and 25 that are adapted to receive bridging switch blades to be hereinafter' described.

As indicated, in Fig. 7, the test switch is of the double-pole type and when a bridging switch blade, to be hereinafter described, connects the contacts 22 or the contacts 23, a-

current path from one pole of a circ-uit is established through contact strips 14 and 17 and the conductor terminals 26 and 27 that are respectively connected thereto.

Vhen the bridging switch blades connect the contact jaws 24 and 25, current path is established from the other pole of the circuit through the contact platesl and 16 that are connected, respectively, to conductor ter minals 2S and 29.

In order to establish connections between the Contact jaws 22 and between the contact jaws 24, a rotary-switch assembly 31 is provided which comprises a substantially square insulating block 32 having its diagonal corners rounded, as indicated in Figs. 6, 7 and 11, and is provided with a cylindrical journal shaft 33 of reduced diameter which is adapted to fit within a circula-r bearing; 34 provided centrally in the end plate 13. The block 32 is provided with a pair of switch blades 35 and 36 that are aligned with the contact aws 22 and 24, respectively, and which engage 1 them when the switch block 32k is in the eX- treme closed position shown in Figs. 1 and 7.

The end plate 13 is provided with a pair of stop members 37 and 33 that are adapted to be engaged by the square corners 39 and 41 of the block 32 when th-e switch is moved to the closed position shown in Figs. 1 and 7, and to limit opening movement of the switch block by engaging the corners after it has been rotated, through` 90, to open position, the square corners 39 and 41 then engaging the stop lugs 38 and 37, respectively. It will be seen, therefore, that rotation of the switch block 32 in a counter-clockwise direction through 90O moves the switch blades 35 and 36 to full-open position.

In order to connect a test instrument in the instrument circuit controlled by the switch, it is desirable to establish the instrument circuit through the test circuit before the switch blades 35 and 36 are moved to open position.

It is apparent from the foregoing that, if bridging switch blades are inserted between the contact jaws 23 and between the contact jaws 25, a circuit will be maintained through the instruments connected to the Switch after the switch blades have been moved to open position.

The test plug for connecting a test instrument in the circuit is illustrated in Fig. 2 and comprises an insulating tube 42 having an enlarged insulating handle 43 that may be detached therefrom when desired. `Within the tube 42, four conductor straps 44, 46 and 47 are mounted, the straps being insulated from one another by means of insulation 48 and retained in assembled relation by means of rivets 49.

As indicated in Fig. 2, the outermost straps 44 are provided with radially extending con-tact blades 51 and 52, respectively, the latter being of greater length thany the former, for reasons that will hereinafter appear. The innermost straps 45 and 46 are respectively provided with radially extending Contact blades 53 and 54, the blade 54 being longer than the blade 53 and the distance between the blades 52 and 54 being the same as the distance between the centers of the contact jaws 23 and 25 of the test switch in order that the blades of the test plug may register with the contact jaws 23 and 25 when the plug is inserted within the test switch.

As indicated in Fig. 2, the conductor strap 48 is connected to a conductor 55, and the conductor strap 47 is connected to a conductor 56, and the conductor straps 45 and 46 are connected, at their ends, to each other by means of a rivet 57. Accordingly the blades 53 and 54 constitute a bridging switch blade for connecting the contact jaws 23, and the blades 51 and 52 are connected to one another through the test instrument (not shown) that is connected between the conductors 55 and 56.

It will be understood that other test arrangements and connections may be made by means of the plug by changing the connections of the conductors 55 and 56 with the conductor straps and by connecting different straps to each other. For instance, the blades 54 and 52 may be made to constitute a bridging switch for a pair of the Contact jaws 23 and 25, in which event, the ends of the conductor straps 47 and 46 will be riveted together, and the conductor 56 will be connected to the conductor strap 45. A variety of test connections may be made by simply changing the connections at the rear end of the test plug.

The test-switch vunit is mounted upon a switchboard panel 57 a having an opening 58 therein of the keyhole type. A front plate 59, made of insulating material and having a keyhole slot 61 registering with the opening 58 in the panel, is secured to the panel by means of screws 62 that extend through the paneland are threaded into threaded sockets 63 in the end plate 12, which is also provided with a keyhole slot 64 that is aligned with. the opening 58 in the panel 57.

By reference to Fig. 3, it will be seen thatthe keyhole slot 61 in the front plate 59 comprises a circular central portion and two relatively narrow end portions 65 and 66,

-the `"latter .'beingilonger than the .Eormer .for permitting the insertion vof the Vlong V'contact blades 4452 and .54 of .the.plug, :thus insuring that'the :plug will be inserted when in .but one position, thereby rendering it impossible :to .so .insert thevplug that improper circuit connections will be made.

The vinner end vof the switch block 32 (Figs. l and 1l) is provided with a transverse notch 67, the Walls of which diverge .from .a .central point to its .outer extremities and the narrow central portion of which is `slightly larger than Vthe width ofthe contact blades f to be hereinafter described.

During the normal operation of the switch,

the bridging switch blades 35 and 36 a-re disposed in the closed positions shown in Figs.

'l and 7. When it is desired to test lthe instru'- ment-associated with the switch, the test plug is inserted until the contact blades 53 and 54 enter the `notch t7 v'in the Vend of the `switch block 32. @At this time, the blades 53 and 54 align with the contact jaws 23, and the blades 5l and 52 align with the contact jaws 25. The block is then rotated in a counter-clockwise direction, as indicated by the arrow in Fig. 3.

Initial rotation of the plug does not im` part movement to the switch block 32, because of the lostnmotion connection therewith, until the blades 5l, 52 and 53 and 54 have entered the switch liaws and 23, respectively, thus establishing a connection through the test instrument before causing disengagement of the switch blades and 36 from the contact jaws 22 and 24.

After the blades 35 and 36 have been disengaged from their respective contacts, current flows through the conductors of the test plug and through the test instrument without kcausing interruption of the circuit through the instrument being tested.

Since the contact blades 51 to 54 of the n test switch are, at this time, between the contact jaws 23 and 25, the test plug cannot be withdrawnlongitudinally. In order to withdraw the test plug, it is iirst necessary to rotate it through substantially o in order to bring the Contact blades 51,52, 53 and 54 into alignment with the transversely disposed keyhole slot 61. This operation irst returns the switch block to its closed position, insuring reestablishment of the original circuit.

The end plate l2 is provided with'four lugs y68, 69, 70 and 71, the latter two being of greater length than the former two and eX- tending across the path of movement Vof the blades 51. and 52 of the test plug to constitute :stops .for limiting the rotary .movement of the plug. The four lugs also -serve -to prevent any .rotary :movement vof the .plug until it Yhas ,been moved to .its operative position wherein the contact blades 5l to '54 -accurately align with the .contact jaws 25 and 23. Referring -to Figs. l, 9 and l0, it will be noted that the end corners of the 'lu-gs 568 and 69are roundedat 7 2 in order to cam the test lug into its extreme inner position in the .plug has reached its innermost position.

By reason of -the lconstruction herein disclosed, instrument .tests are greatly facilitated, `and it is `not necessary toconnecty wires tothe switch through the lmedium of test connections exposed at the iront of 'the switch-V board panel, as has been the present practice. In the usual switchboard installation, a

large number of instrumentsare arranged in a horizontal row along the switchboard and, 4by reason of this construction, lthe opera-tor may move along theswit'chboard and `rapidly insert the test plug` and take readings on the .successive instruments inl a very shorttime. The arrangement is such that, where necessary, simultaneous tests of instruments may be made when conditions so require, by arranging .a plurality of test plugs within the test switches and connecting the' test'plugs with va mechanical driving connection for simultaneously rotating the plugs.

Vhile I have illustrated only one embodiment of my invention, rit will be apparent to those skilled in the art that various changes, modifications, substitutions, additions and omissions may be made i-n the apparatus illustrated without departing from fthe spirit and scope of myinvention as set lforth in the appended claims.

I claim as myinven'tion':

l. The combination. with a 'test switch thavying a plurality of contacts and a movable 'switch member for engaging `certain of the said contacts, of a rotatable test plug having means for operatively engaging the movable `switch member when moved 4in an axial direction and having switch members for engaging other of the said contacts when rotated for Amoving the switch member.

2. The combination with a test switch having av `plurality of contacts and a rotatable switch member Jfor engaging certain of the said contacts, of a rotatable test plug having means for operatively engaging the movable switch rmember when moved in-an aXialdirection and having switch members so disposed that they engage other contacts when rotated for moving the switch member and before the latter is moved out of engagement with its respective contacts.

3. Test-switchmechanism comprisingasupport, la plurality of contacts on the support,

a rotatable contact mounted on the support and movable into engagement with certain 35 event that it is rotated slightly before the of the contats, and a rotatable test plug for operatively engaging the movable contact when moved in an axial direction and whereby rotary movement of the plug imparts rotary movement to the movable contact, and a. contact on the plug for engaging the other contacts when rotated -for moving the rotatable contact.

4. Test-switch mechanism comprising a support, a plurality of contacts on the support, a contact mounted on the support and rotatable into engagement with certain of the contacts, and a rotatable test plug 'for operatively engaging the movable contact when moved in an axial direction and whereby rotary movement of the plug imparts rotary movement to the rotatable Contact, and a contact on the plug for engaging the other contracts when rotated for moving the rotatable contacts and before the latter is disengaged from its respective contacts.

5. Test-switch mechanism comprising a support, a plurality of contacts on the support, a rotatable switch mounted on the support for engaging certain of the said contacts, a rotatable test plug having contacts for engaging other of said contacts adapted to be inserted in the support by a longitudinal movement of the plug and provided with means for engaging the rotatable switch whereby the switch is rotated with the plug, the said contacts of the plug being so disposed that they engage their respective contacts only when rotated and before the switch is disengaged from its respective contacts.

6. A test switch comprising a pair of end members, a pair of Contact plates for connecting the end members and retaining them in assembled position, contacts mounted upon the said plates, a movable switch mounted on one of the members for engaging certain of 4the said contacts, and a test plug removably supported by the other member for engaging and operating the switch member and having a Contact thereon for engaging other of the said contacts.

7. A switch comprising a pair of end members, four interchangeable contact plates for joining the end members and for retaining them in spaced relation, the said plates having contacts so disposed that they are aligned in two separate rows between the said end members, and a switch carried by an end member having contacts for engaging a contact of each row.

8. A test switch comprising a support, a plurality of contacts mounted on the support, a rotatable switch mounted on the support for engaging certain of the said contacts, a removable test plug mounted upon the sup port for longitudinal and rotary movement and movable longitudinally into operating engagement with the switch, and rotatably movable into engagement with the other of the said contacts, the said contacts on the plug preventing longitudinal disengaging movement of the 'plug so long as they are in engagement with the said other contacts.

9. A test switch comprising a support, a plurality of contacts mounted on the support, a rotatable switch mounted on the support `for engaging certain of the said contacts, a removable test plug mounted upon the support for longitudinal and rotary movement and movable longitudinally into operating engagement with the switch, and rotatably movable into engagement with the other of the said contacts only when in operative relation to the switch.

l0. A test switch comprising a pair of end members, a pair of contact plates for connecting the end members and retaining them in assembled position, contacts mounted upon the said plates, a movable switch mounted on one of the members for engaging certain of the said contacts, a test plug movably supported by the other member for engaging and operating the switch member and having a contact thereon for engaging other of the said contacts, and means on the end members for limiting rotary movement of the switch and the plug.

In testimony whereof, I have hereunto subscribed my name this 26th day of October,

VALTER H. SCHRAMM. 

